The front of motor vehicles has a structure in which the windshield, the hood and the bulkhead separating the engine compartment from the passenger compartment meet. The window opening lower crossbeam is secured to the bulkhead in such a way as to be able to support the windshield on which the latter rests. Hence, the lower crossbeam is installed transversely and, according to the vertical and longitudinal components of the vehicle, extends between a lower edge of the windshield and the bulkhead which itself extends substantially plumb with said windshield. In order to perform its role of supporting the windshield, the window opening lower crossbeam has to be sufficiently strong. Hence it usually comprises two transverse parts combined with one another, an upper window opening lower crossbeam and a lower window opening lower crossbeam, so as to form a transverse box structure, or hollow body, on which the lower edge of the windshield rests directly. To do this, of the two transverse parts, a first part having a fixing transverse edge and, opposite, a receiving transverse edge, is fitted between the bulkhead and the windshield. The first part constitutes the upper window opening lower crossbeam. The fixing edge is therefore engaged on the bulkhead, while the lower edge of the windshield rests in the receiving transverse edge. The second transverse part of the crossbeam, which has a transverse connecting edge and an opposite transverse resting edge, is fitted against the first part in such a way that the connecting edge is connected to the first part between the first fixing edge and the first receiving edge of the first part and that the resting edge is connected to the receiving transverse edge of the first part, thereby forming a tubular element therewith, which tubular element constitutes the transverse box structure. The second part constitutes the lower window opening lower crossbeam. As a result, the lower edge of the windshield is held directly by the transverse box structure which itself rests laterally in the structure of the motor vehicle, and notably on the shock-absorber cups.
Moreover, the connecting edge of the second transverse part divides the first part into a receiving portion which extends toward the receiving edge thereby forming one wall of the transverse box structure and an opposite fixing portion which extends toward the fixing edge of the first part and which meets the bulkhead. This fixing portion is, by nature, deformable and in the event of a pedestrian impact, i.e. in the event of the relative movement of an individual toward the windshield of the vehicle, allows the windshield precisely to be able to push in in order to dissipate some of the mechanical energy generated by the impact and thus as far as possible safeguard the vital parts of said pedestrian, notably the pedestrian's head.
Reference may be made to document U.S. Pat. No. 6,193,304 which describes such a shock-absorbing lower crossbeam.
However, the transverse box structure which is required for supporting the windshield limits the ability of the aforementioned fixing portion to deform and, at the same time, limits the possibilities for dissipating the energy generated by the impact.
So, one problem which arises and which the present invention seeks to overcome is that of supplying a window opening lower crossbeam which, while supporting the windshield of the motor vehicle, has a better ability to deform in order to safeguard individuals in the event of an impact.